Some tips
You need to place four lines, like a frame, each 1km long, around the part of the Google earth area you want to have attached to your basemap. Use the GE ruler tool, select Line and metres. Pull each line to exactly 1000m. To ensure that your N/S and E/W lines are truly vertical and horizontal watch the bearing in the ruler box and keep them to the required angle, i.e. 0⁰ or 180⁰ for N/S (depending on which end you start at), and 90⁰ or 270⁰ for your E/W lines.
The GE view height is irrelevant at this stage. Just use the best height the get that square accurately laid, which is usually high up to start with and very close in to join up each subsequent line where they meet at the corners.
Remember to name and save each line.
Use the Google earth rotate/reset function (the R key) which will force the GE image to be absolutely vertical and north up. That will make your lines easier to lay accurately, as will going to Tools>Options>Elevation Exaggeration and changing the default (1.5) to 0.01. That will smooth out the hills and allow your square to lay flat.
Once the square is accurately marked then, and only then, should you attempt to copy it.
I go to 600m elevation which provides a very clear image, but at this height you will only see part of the square. You therefore need to move around cutting the various sections and pasting it into your graphics package. I find MS-Paint easiest for this job. I open two instances of Paint. One to drop in the bits of the 1km square from GE which I then trim and then copy into the second Paint where they are all joined together. From memory there are six cuts required to piece them all together.
It’s important to keep to the 600m height. Any variation between each of the sections will result in misalignment.
Here's a link to a thread where I posted some additional stuff on the subject.
